Patent GB-251110-A (GB)
Title: Improvements in light projecting and advertisement displaying apparatus
IPC: G02B27/06
Filed: 1925-05-09
Abstract: 251,110. Abel, A. May 9, 1925. Optical-projection apparatus. - In apparatus wherein optically-projected light is directed by a universallypivoted mirror in a series of directions in sequence, means comprising a slowly and uniformly rotating con troller disc transmitting jerks to a main shaft are provided for effecting the change of direction &c. of the beam comparatively instantaneously. The mirror 5 is tilted by a vertically-moving bar 24 and horizontally rotated by a lever controlled respectively by cams 15 and 16 fixed on the main shaft 14. A cam 17 controls an iris diaphragm 18, and a cam wheel 36 intermittently advances a colour disc 40 and a diapositive disc 119, both mounted on a shaft 39. The cams 15, 16, 17 are provided with aprons 22, Fig. 8 adjustable by set screws 79 to control the movements of the mirror 5 and diaphragm 18. Means are described for turning the screws 79 from a distant point consisting of a box spanner 86, Fig. 9 moved towards the screw 79 by a spring 89 under control of a handle 91, and rotated by a tensioned chain 92 passing over a wheel 81. The cam wheel 36 rocks a lever 95, Fig. 11, which oscillates bellcranks 98, 99 carrying a pawl 100 which engages a ratchet wheel 101 fixed to the colour disc 40. To position the disc 40 a ratchet wheel 104 is engaged by a stationary pawl 105 which is lifted before movement of the disc 40 by depression of its tail 106 by a pin &c. 107 on the crank 99. A spring detent 105a prevents return of the disc 40. The diapositive carrier 119 is slidably fixed on the shaft 39 for focussing purposes and a similar arrangement of pawls &c. as that used for actuating the colour disc is employed, with the addition of a cam surface which prevents turning of the carrier except at every sixth impulse. The carrier 119 is provided with three arms, at the end of each of which a diapositive. is supported in a rotatably adjustable manner. A cam actuated mercury switch is employed to divert the electric current at intervals from the projector lamp 2 to a general illuminating lamp. In a modified form of projector the lamp is combined with a lens or mirror reflector, and the whole adapted to swing, the size of the light cone being determined either by an iris diaphragm or by shifting the lamp along the optical axis of the mirror by a Bowden wire controlled from a cam on the shaft 14. At every movement of the mirror 5 the light is cut off by a shutter 45 actuated by a cam ring 42 on the cam 17. The ways of effecting rapid movement of the mirror, diaphragm, &c. are described. Fig. 4 shows a continuously rotating gear wheel 13 mounted loosely on the shaft 14 and having fixed to it a toothed controller disc 47 and a projecting pin to which is attached one end of a helical spring 51, connected at its other end to the shaft 14. A ratchet wheel 48 fixed to the shaft 14 has a slot which takes over the pin, and the disc 47 and wheel 48 are engaged by two pawls which are connected together by a link disengagable by the wheel 48. Rotation of the disc 47 forces out both pawls till the wheel 48 is released and the shaft 14 is turned quickly by the spring 51 through the space of one tooth, the disengaged link allowing the pawl to be brought back by a spring to re-engage the wheel 48. The alternative method described consists of a clutch 64, 70, Fig. 6, which is thrown into gear by a cam 66 acting on a pivoted spring-pressed clutch arm 68. A pawl controlled by the cam disc 64a engages teeth in the cam circumference to position the shaft 14 through the medium of the clutch.